Mutations in Complement Factor H Impair Alternative Pathway Regulation on Mouse Glomerular Endothelial Cells in Vitro

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Loeven , M A , Rops , A L , Lehtinen , M J , van Kuppevelt , T H , Daha , M R , Smith , R J , Bakker , M , Berden , J H , Rabelink , T J , Jokiranta , T S & van der Vlag , J 2016 , ' Mutations in Complement Factor H Impair Alternative Pathway Regulation on Mouse Glomerular Endothelial Cells in Vitro ' , Journal of Biological Chemistry , vol. 291 , no. 10 , pp. 4974-4981 . https://doi.org/10.1074/jbc.M115.702506

Title: Mutations in Complement Factor H Impair Alternative Pathway Regulation on Mouse Glomerular Endothelial Cells in Vitro
Author: Loeven, Markus A.; Rops, Angelique L.; Lehtinen, Markus J.; van Kuppevelt, Toin H.; Daha, Mohamed R.; Smith, Richard J.; Bakker, Marinka; Berden, Jo H.; Rabelink, Ton J.; Jokiranta, T. Sakari; van der Vlag, Johan
Contributor: University of Helsinki, Department of Bacteriology and Immunology
University of Helsinki, Medicum
Date: 2016-03-04
Language: eng
Number of pages: 8
Belongs to series: Journal of Biological Chemistry
ISSN: 0021-9258
URI: http://hdl.handle.net/10138/161078
Abstract: Complement factor H (FH) inhibits complement activation and interacts with glomerular endothelium via its complement control protein domains 19 and 20, which also recognize heparan sulfate (HS). Abnormalities in FH are associated with the renal diseases atypical hemolytic uremic syndrome and dense deposit disease and the ocular disease age-related macular degeneration. Although FH systemically controls complement activation, clinical phenotypes selectively manifest in kidneys and eyes, suggesting the presence of tissue-specific determinants of disease development. Recent results imply the importance of tissue-specifically expressed, sulfated glycosaminoglycans (GAGs), like HS, in determining FH binding to and activity on host tissues. Therefore, we investigated which GAGs mediate human FH and recombinant human FH complement control proteins domains 19 and 20 (FH19-20) binding to mouse glomerular endothelial cells (mGEnCs) in ELISA. Furthermore, we evaluated the functional defects of FH19-20 mutants during complement activation by measuring C3b deposition on mGEnCs using flow cytometry. FH and FH19-20 bound dose-dependently to mGEnCs and TNF- treatment increased binding of both proteins, whereas heparinase digestion and competition with heparin/HS inhibited binding. Furthermore, 2-O-, and 6-O-, but not N-desulfation of heparin, significantly increased the inhibitory effect on FH19-20 binding to mGEnCs. Compared with wild type FH19-20, atypical hemolytic uremic syndrome-associated mutants were less able to compete with FH in normal human serum during complement activation on mGEnCs, confirming their potential glomerular pathogenicity. In conclusion, our study shows that FH and FH19-20 binding to glomerular endothelial cells is differentially mediated by HS but not other GAGs. Furthermore, we describe a novel, patient serum-independent competition assay for pathogenicity screening of FH19-20 mutants.
Subject: autoimmune disease
complement system
endothelium
heparan sulfate
innate immunity
atypical hemolytic uremic syndrome
complement Factor H
endothelial glycocalyx
HEMOLYTIC-UREMIC SYNDROME
HUMAN-ERYTHROCYTE MEMBRANE
HEPARAN-SULFATE
BINDING-SITES
MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS
BETA-1H GLOBULIN
PROTEIN BETA-1H
C-3 CONVERTASE
BOUND C3B
2 PARTS
3111 Biomedicine
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